When a 100' multi-limb creature tries to grab you, you might move quite quickly and passionately too...

May even impress an experienced track-and-field coach if one happens nearby...
Seriously though, those are double good news. His immune system was able to handle the parasitic and bacterial cultures of your outside pond, which are quite different from your tank and his place of evolution/origin. I'd place him in QT for a couple of months and maybe even consider a prophylactic, wide-spectrum anti-parasitic treatment.